In differentiated cells (e.g. liver and fibroblast cultures) the biosynthesis of dolichol appears to be regulated at the level of HMG-CoA reductase. However, in some differentiating tissues (e.g. erythropoietic spleen and developing brain), another mechanism for regulating dolichol and dolichyl phosphate synthesis independent by of HMC-CoA reductase activity comes into play. A high rate of dolichyl phosphate synthesis at a particular stage in cellular differentiation may reflect a requirement for N-linked glycoproteins that are involved in cell-cell interactions or that have other functions in the differentiation process. The present proposal has the following major objectives: I. To determine the existence, production and utilization of reserve stores of dolichol. Studies will include (a) measurements of the concentrations of dolichol and its derivatives and of the rates of their production from [14C]-acetate in various differentiated and differentiating cells and tissues, (b) measuremens of the production and utilization of dolichol and its derivatives in liver and fibroblast cultures under conditions wherein dolichol synthesis is stimulated or severely inhibited. II. To investigate the regulation of dolichol and dolichol and dolichyl phosphate biosynthesis and its relationship to glycoprotein biosynthesis in differentiating tissues. These studies will emphasize measurements of the enzyme activities: prenyl transferase, dolichol phosphokinase, dolichyl phosphate phosphatase and dolichyl acylesterase and of saccharide incorporation into N-linked glycoproteins in various differentiating tissues. III. To assign the high rate of dolichol and dolichyl phosphate synthesis seen in spleens of phenyhydrazine-treated mice to one or more particular stages of hemopoiesis and IV. To investigate the regulation of dolichol biosynthesis and the role of dolichol in the induced differentiation of cultured Friend erythroleukemia cells, human promyelocytic leukemia (HL-60) cells and embryonal carcinoma cells. The results of these studies may lead to a better understanding of the regulation of differentiation and of the specific role of dolichol and N-linked glycoproteins in the process.